2. Dynamics of Nanoparticles (borrowing, as Nano often does, from Macromolecular) Techniques Problems Your career = Techniques X Problems Tomas Hirschfeld: Most people work only on techniques, but not on finding problems. But remember, your career will be the vector cross product of techniques you learn and problems you choose. This talk concerns

3. Why do we need dynamics for nanoparticle characterization? 1. Dynamics give us size Microscopy does not always measure size well. Microscopy cannot follow rapid size/shape changes well—e.g. self-assembly. Microscopy may alter the materials being studied. Small angle X-ray scattering and small angle neutron scattering are slow, expensive, can damage samples, and sometimes have contrast issues. 2. Dynamics tells us basic information Stability of structures: scaffolds to slow the kT problem Internal viscosity inside devices: how fast can nanodevices work?

4. Dynamics Techniques  DLS = Dynamic light scattering  FPR = Fluorescence photobleaching recovery  AUC = Analytical ultracentrifugation  DOSY = Diffusion ordered NMR spectroscopy (not this trip—takes too long to explain)

5. DLS = Dynamic Light Scattering If you look closely at light scattered by a sample, it fluctuates. Some of that is just DUST, a nuisance, but some fluctuations are interesting. The fluctuations represent how quickly the molecules are moving. This is tracked with a “correlation function”

6. Correlation Function Where E(t) is the instantaneous electric field of the scattered light E(t)E(t) t’ t = 0 t =  0 Thus, correlation Functions DECAY with time!

7. Quick decay = fast mover = small particle t g (t )g (t ) Slow, big Fast, small  = decay rate (Hz)

8. An exponential becomes a sigmoidal curve if you change the x-axis to logarithmic. Log( t ) g (t )g (t ) Slow, big Fast, small  comes from inflection point.

9. Dynamic Light Scattering  Hv = q 2 D trans + 6D rot LASERV H  PMT Hv Geometry (Depolarized) Uv Geometry (Polarized) V   Uv = q 2 D trans PMT LASER

10. FPR = Fluorescence Photobleaching Recovery First, measure fluorescence: step F Then photobleach (“erase”) some with a bright flash of light: step P Then observe recovery due to diffusion: step R The sample has to be fluorescently labeled. Destruction of the label must not damage the nanoparticle.

11. Fluorescence & Photobleaching Blue input light Fluorescent Sample Green Detected Light

12. Recovery of Fluorescence Blue input light Fluorescent Sample With Fluorescence Hole in Middle Green Detected Light Slowly Recovers

13. Modulation FPR Device Lanni & Ware, Rev. Sci. Instrum. 1982 * * * * AOM M M D RR DM OBJ S PMT PA SCOPE TA/PVD ARGON ION LASER * = computer link IFIF XX c 5-10% bleach depth

14. Cue The Movie

15. The FPR contrast decay resembles DLS. t Contrast (t ) Slow, big Fast, small  = decay rate (Hz)

16. AUC = Analytical Ultracentrifugation—a Good Way to Characterize Self-assembled Species Rotor (side perspective) Spins at up to 60,000 rpm Sealed dual beam UV-Vis cell

17. Sedimentation: simple gravity + thermo  FbFb FdFd FcFc r r = a; meniscus r = b; bottom Svedberg Nobel Prize Chemistry, 1926

18. OK, so let’s look at 5 applications 1. Can we measure the viscosity in a nanoreactor? (DLS) 2. Can we watch a bio/nano particle change? (DLS & LS) 3. Nanotech needs scaffolds: will they stand still? (FPR) 4. Controlling self assembly. (DLS) 5. Making a word using one of the most fascinating of the new nano alphabets. (AUC) Some of this is published: See http://macro.lsu.edu/russo  research articles linkhttp://macro.lsu.edu/russo

19. ZADS = special form of DLS PTFE latex microrheology of polyacrylamide gel Camins & Russo, Langmuir, 4053, 1994 See also: Piazza, Tong, Weitz 1 PTFE Particles ~ 250 nm

20. More ZADS 1

21. Seedlings  Sick Plants  And close-up of mosaic pattern. http://www.uct.ac.za/depts/mmi/stannard/linda.html 1

22. What we have been trying to do: rotation and translation of a TMV through “random coil” solutions. Very hard to do right! 1. Cush et al. Macromolecules 1997. 2. Cush & Russo Macromolecules, 2004 (in press, probably December) 1

23. D rotation ~  -1 & D translation ~  -1 Bottom line: TMV or nanoparticles can report the viscosity more or less accurately in a small system. 1

24. “Virions are usually roughly spherical and about 200nm in diameter. The envelope contains rigid "spikes" of haemagglutinin and neuraminidase which form a characteristic halo of projections around negatively stained virus particles. “ Linda StannardLinda Stannard, of the Department of Medical Microbiology, University of Cape Town http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html “The Flu” 2

25. Guinier plots. I LS vs. q 2 pH 7.4 900 Å pH 5 1330 Å pH 5 later 1710 Å 2

26. Dynamics of Flu “opening up”: Addition of citric acid for pH change is shown by the line at time 0. 2

27. Sproing!!! pH  2

28. Forms a reversible gel scaffold. PSLG: poly(stearyl-L-glutamate) 3

29. Temperature-ramped modulation FPR 3

30. Everything can move, yet the structure remains. Means that even though you have built a scaffold (for example, to grow artificial skin or hold a sensor or drug delivery nanomachine in place) and even though it may seem to hold its shape, you must be careful! This kind of molecular view of gelation is not available from mechanical methods, such as rheology. 3

31. Observe Control of Self-assembly Bolaform amphiphiles have a dumb-bell shape hydrophilic hydrophobic 4

32. Arborol example: [9]-10-[9] 9 watery hydroxyl groups 10 oily methylene groups 4

33. Arborol properties Dissolve in warm water. Gel on cooling— Why? How? Apparently, they are “real gels” Fibers inside the gels. Self-assembly Reversible 4

34. Why do we care? Self-assembling system Reversible Easy to vary headgroup and core size Possible applications in: Porous media Stationary phase for separations Reversible, rigid rods  dynamic liquid crystals we can manipulate Disease-inspired microfluidics—can we simulate sickle cell anemia? 4

35. Dendrimer self-assembly challenges Can we control self-assembly? Synthesis! How would we know? Analysis! What if we did? New Physics & Materials! Terminator 4

36. Self-assembly of [9]-12-[9] by DLS Self-assembly of Dilute Arborols—R h R h got from linear fit of gamma vs q 2 of DLS data at five angles: 40, 50, 60, 70 and 90. 4

37. New problem: Hexaruthenium terpyridyl supramolecular structures 2 is the key monomer for the supramolecule. 5 aids in Proof of structure. Newkome et al. Angew.Chem.Int.Ed. 1999, 38(24) 3717-21 5

38. Molecular snowflake by two methods 5

39. Data on supposed snowflake supports several scenarios, but self assembly surely occurs Same Data, Different Analysis 0.5% (NMR conc.) 80% @ M=1340M=3250 20% @ M=5600+ non-sedimenting stuff 0.006% (low!) M = 2600 5

40. Write the terpyridyl aggregate in shorthand form.  5

41. We see evidence of aggregation by SAXS, confirmed by DLS. n Stacked disks? Continue In this way to make aggregates of aggregates of aggregates etc. Note that this alphabet retains symmetry similar to the atomic alphabet ? 5

42. Conclusions The power of DLS, FPR and AUC has been demonstrated. It was my purpose to familiarize you with these tools….but maybe I accidentally showed you some good problems to study as well. Maybe you can see a new vector cross product somewhere. The terpyridyl ruthenium business is an example of a supramolecule; however, the proponents of supramolecular thinking have less influence than the nano people. So…it must be nano!